Optical properties of cobalt/nickel doped SrAl12O19 blue inorganic pigments and their application in 3YSZ ceramics

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Colored zirconia ceramics are widely used in high-end applications; however, the range of pigments capable of achieving coloration throughout the material remains limited. In this work, cobalt/nickel doped magnetoplumbite-type strontium hexaaluminates, SrAl 12- x Co x O 19- δ (0 ≤ x ≤ 0.4) and SrAl 12- x Ni x O 19- δ (0 ≤ x ≤ 0.3), were successfully synthesized via solid state reaction, yielding vivid blue inorganic pigments with low cobalt/nickel content and excellent chemical stability. The striking ocean blue hue in cobalt doped SrAl 12 O 19 originates from the d-d transition A 2 4 ( F 4 ) → T 1 4 ( P 4 ) of tetrahedrally coordinated Co 2 + , while the sky blue shade in nickel doped samples is attributed to the T 1 3 ( F 3 ) → T 1 3 ( P 3 ) transition of tetrahedral Ni 2+ . These pigments (5–10 wt%) were incorporated into the 3 mol% yttria stabilized zirconia (3YSZ) matrix and sintered at 1400 °C to prepare blue 3YSZ ceramics. SEM and EDS analyses revealed that the pigments maintained their structural stability and coexisted with zirconia as a secondary phase even after high temperature sintering. Furthermore, the Vickers hardness of the as-fired blue 3YSZ ceramics was slightly enhanced compared to pure 3YSZ, demonstrating both aesthetic appeal and mechanical stability. • Novel blue 3YSZ ceramics were synthesized through a solid state reaction. • Chromophores are Co/Ni doped SrAl 12 O 19 pigments with magnetoplumbite structure. • The blue color arises from d-d electron transitions in Co 2+ /Ni 2+ tetrahedral sites. • The chromophores have excellent chemical stability and coexist with 3YSZ. • Blue 3YSZ ceramics show excellent blue effect and stable mechanical properties.